| The rapid development of the computer network not only brings a lot of convenience, but alsogreat security threats. The traditional cryptography has much difficult in meeting the requirements ofinformation security of complexity and diversity. Information hiding technique which utilizesredundant features of the carrier signal and insensitivity of the human visual auditory system hidessecret information even covers up the fact that secret information is being transmitted. Based on thestudy of information hiding techniques and the consideration of the existing problems and risks ofsecret information transmission, an information hiding system which is based on orthogonal fractalcoding has been designed in this paper. The main contents of this paper are as follows:Firstly, an improved digital watermarking algorithm for color images which is based onorthogonal fractal coding is proposed. It utilizes the correlation among the R,G,B components of thecolor image to encode the luminance component of color image. Compared to encoding the threecomponents separately, it reduces the time spent on encoding procedure by modifying the codingparameter of the three components. At the sanme time, taking advantage of collage error and thetransformation function, the proposal algorithm embeds the gray watermarking image into carrierimage. What’s more, it realizes the blind extraction and enhances the transparency and robustness.Secondly, based on the research of quad-tree segmentation and orthogonal fractal watermarkingalgorithm, this paper proposes an information hiding algorithm with quad-tree segmentation. The newalgorithm uses quad-tree segmentation to split the carrier images, and encodes the split blocks byorthogonal fractal coding. And then it embeds the secret image into carrier image by modifying theparameters of orthogonal fractal coding. Additionally, it takes into account of the amount informationhiding and hidden time consuming. Simultaneously, most of the information hiding algorithm rarelyconsider the merits of the carrier image. This paper uses average collage error as a screening measureof the carrier image, so the quality of the decoded image is ensured somehow and enhancesconcealment of hidden information.Finally, the main modules of information hiding system are designed and implemented. And it ispreliminary conducted on a ship-shore communication system. Practice has proved that this systemcan successfully complete the mission of secret images transmission under the condition of normalcircumstances and a third-party interception and attacks. |
